Gasoline service stations typically include a number of underground storage tanks for storing fuel products. A conduit known as a riser line generally extends from the top of each tank to a manhole at the driveway surface of the service station. A drop tube may be concentrically disposed within the riser line, flush with the riser line at the surface but extending beyond the riser line and into the underground storage tank. By removing the manhole cover and a cap from the top of the riser, a hose can be connected to the riser line to fill the product tank with petroleum products delivered by tanker trucks. The hose is generally connected to the riser line using a connector known as a top seal delivery nozzle. Such nozzles allow the hose to be quickly connected and disconnected from the riser line at a fill adapter located on the top of the riser line to simplify product transfer. These fill adapters are typically threaded to the riser line which is in turn threaded into a collar on the top of its respective product tank. When the underground storage tank is not being filled, a removable cap is used to seal the fill adapter both to prevent contaminants from entering the product tank and to prevent hydrocarbon vapors from escaping from the tank.
One problem with the use of conventional top seal delivery nozzles is that while no twisting is required to fasten the nozzle to the fill adapter, during the transfer of product, especially at the end of the product transfer when the hose is lifted and drained of any remaining product, some twisting of the nozzle occurs. Such twisting of the hose can cause twisting of the fill adapter, loosening it from the riser line. To prevent such loosening of the fill adapter from the riser line, fill adapters are often equipped with set screws which lock them to the riser line. While such a practice prevents the fill adapter from loosening from the riser, it can cause twisting of the entire riser. This can sometimes cause the riser to loosen from the tank collar. The loosening of any of the fittings or connectors on the riser line is to be avoided as it can lead to product or vapor leakage, or product contamination.
At least one known swivel fitting has been developed for fill adapters to permit rotation of the nozzle with respect to the riser line without causing any loosening of either the connection between the fill adapter and riser line, or the riser line and underground storage tank. One such fitting is sold by OPW Fueling Components of Cincinnati, Ohio, and is illustrated in U.S. Pat. No. 5,664,951.
The '951 patent discloses a two-piece swivel adapter which uses a flexible, electrically conductive rod to rotatably couple the two pieces of the adapter. However, the rotation achieved by this swivel adapter can be rough. Thus there exists a need for an improved swivel fitting which provides smooth and even rotation.